As an example of systems for temporarily repairing a flat tire, a system has been known that has a pressure-proof container containing a puncture sealant and a high pressure air source such as a compressor (hereinafter referred also to as the integrated system) (see, FIG. 1 of Patent Document 2). In this system, the puncture sealant is injected through an air valve into a tire, and then high-pressure air is continuously injected until the tire is pumped up to a sufficient pressure for driving.
Puncture sealants of this kind prepared by blending a resin tackifier and ethylene glycol with a natural rubber latex have been proposed as described in Patent Documents 1 to 3. In the case of the puncture sealants including a natural rubber latex as a base and ethylene glycol as an antifreezing agent, creaming tends to occur in a long time storage. Therefore, improvement of the storage stability (long-term storability) of the puncture sealants has been demanded.
In order to solve the problem, Patent Document 4 has proposed a puncture sealant in which propylene glycol is used as an antifreezing agent for improving the stability. The concentration of the propylene glycol in a liquid portion of a conventional puncture sealant is approximately 50%. Use of the conventional puncture sealant at a temperature of −30° C. is guaranteed. However, the viscosity of the puncture sealant drastically increases at a temperature below a certain temperature, and the puncture sealant may be “frozen” at such a temperature. Therefore, in consideration of use in extremely cold regions, puncture sealants which can also be used at a further lower temperature have been demanded. Although the fluidity of puncture sealants can be improved by reducing the amount of the solid components such as rubber particles and a tackifying resin, problematically, puncture sealing performance may be then deteriorated. Further, in the case of use in the integrated system, puncture sealants may be coagulated in the air valve at high temperatures, and thus the pressure of the tire cannot be increased to a predetermined pressure level.    Patent Document 1: JP-A 2002-294214    Patent Document 2: JP-A 2001-198986    Patent Document 3: JP-A 2000-272022    Patent Document 4: JP-B 4074073